Nature and Science, 2012;10(2) http://www.sciencepub.net/nature Investigation on defensive enzymes activity of Brassica juncea genotypes during pathogenesis of Alternaria blight Pankaj Singh Parihar, Om Prakash and H. Punetha* Department of Biochemistry College of Basic Sciences and Humanities Department of Chemistry College of Basic Sciences and Humanities G.B. Pant University of Agriculture and Technology, Pantnagar 263145 (Uttarakhand) India. [email protected], [email protected] ABSTRACT: The investigation was carried out to know the biochemical basis of defense mechanism of seven Brassica juncea genotypes infected with Alternaria blight, under field conditions. Genotypes EC-399299, EC- 399296, EC-399313 and PHR-2 showed lowest percent Disease Severity Index. The activity of PAL, PPO, Peroxidase and Catalase were recorded at 65DAS, 25DPI and 50DPI. Biochemical analysis of infected genotypes revealed an increase in PAL, PPO and peroxidase activity. EC-399299, EC-399296 and PHR-2 exhibited maximum increase in these parameters. Catalase activity was decreased, with the progresses of disease. The activity of PAL, PPO, peoxidase and catalase were used as parameter to identify the resistant genotype for breeding programmes. The finding revealed that EC-399299, EC-399296, EC-399313 and PHR-2 are comparatively more resistance against infection of Alternaria brassicae then other observed genotypes and suggested that PAL, PPO and peroxidase may play an important role in under taking the defense mechanisms of Brassica juncea genotypes against Alerternaria blight pathogenesis. [Pankaj Singh Parihar, Om Prakash and H. Punetha. Investigation on defensive enzymes activity of Brassica juncea genotypes during pathogenesis of Alternaria blight. Nature and Science 2012;10(2):63-68]. (ISSN: 1545-0740). http://www.sciencepub.net. 11 Key Words: Brassica juncea, Alternaria blight, defensive enzymes INTRODUCTION hypersensitive response, lignification, cross-linking of Alternaria blight disease caused by Alternaria phenolics and glycoprotein, suberization and brassicae (Berk.) Sacc has been reported from all the phytoalexin production. Catalase is frequently used continents of the world and is one the important by cells to rapidly catalyze the decomposition of devastating diseases of Indian mustard causing up to hydrogen peroxide into less reactive gaseous oxygen 47% yield losses “(Kolte, 1986)”. Average yield losses and water molecules thus avoiding cellular in the range of 32-57 per cent due to Alternaria blight disintegration “(Bolwell and Wojtaszek, 1997)”. The have been reported “(Shrestha et al., 2005)”. In present investigation focused on biochemical changes addition to the direct losses in yield, the disease in susceptible and resistant cultivars of Brassica juncea adversely affects the seed quality by reducing seed size, during pathogenesis of Alternaria brassicae. seed discolouration and reduction in oil content “(Prasad & Lallu, 2006)”. The host-pathogen MATERIALS AND METHODS interaction induce signaling molecule in plants system, The investigation was carried out at Crop which lead to production of antimicrobial compound. Research Centre, G.B.P.U.A & T., Pantnagar during Defensive enzymes are among the most influential and rabi season, 2010-2011. Seven genotypes of Brassica widely distributed products in the plants. PAL, PPO juncea namely EC-399313, EC-399312, EC-399296, and peroxidase were reported in plants treated with EC-399299, 399302, PHR-2 and Varuna were used for various biotic and abiotic inducer “(Raghvendra et al., the present investigation. For all biochemical analysis 2007)”. Phenylalanine ammonialyase (PAL) is the key fresh leaf samples were used. The experiment was laid enzyme catalyzing the biosynthesis of phenolics and out in a randomized block design (RBD) with three lignin from the aromatic amino acid phenylalanine replications. “(Cartea et al., 2010)”. Polyphenol oxidase (PPO) is Phenylalanine ammonia lyase (PAL) activity allowed to leave the chloroplast thylakoid membrane was measured as described by “(Lisker et al, 1983)”. and come in contact with the accumulated phenolic Leaf material was homogenized in 25mM Tris-HCI compounds. In the presence of oxygen, PPO oxidizes buffer, pH 8.8 (w/v, 1:1) centrifuged at 8000 r.c.f for the phenolic compounds that are in the form of o- 30 min at 4°C. The reaction mixture contains 1 mL of diphenol to a o-quinone(Raj et al., 2006). The plants enzyme extract, 0.5 mL substrate L-phenylalanine and 0.4 peroxidases have been implicated in a variety of mL of 25mM Tris-HCL buffer (pH 8.8). After incubation defense-related processes, including the of 2h at 40°C, activity was stopped by the addition of 63 Nature and Science, 2012;10(2) http://www.sciencepub.net/nature 0.06mL 5N HCL and the absorption was read at 290nm. 25DPI and 50 DPI respectively, whereas highest The enzyme activity was expressed as µmol of trance – activity observed in EC-399299 (8.77, 10.77 and cinnamic acid /mg of protein/h. Polyphenol oxidase 12.6 µmol of trans-cinnamic acid/mg protein/h) at activity measured as described by “(Mayer et al, 65DAS, 25DPI and 50DPI respectively followed by 1965)”. Leaf material was homogenized in 50mM EC-399296. Similar observations were recorded in sodium phosphate buffer, pH 6.8 (w/v, 1:1) centrifuged previous research, during the plant development, cell at10,000 r.c.f for 20 min at 4°C The reaction mixture differentiation, stress conditions such as irradiation, contains l00µL of enzyme extract, 50µL of substrate wounding, nutrient deficiencies, herbicide treatment and 60mM catechol and 2mL of 50mM sodium phosphate viral, fungal and insect attacks ” (Morelló et al., 2005)”. buffer (pH 6.8). The absorption was read at 290nm Logemann et al. (2000) reported that the increase in PAL enzyme activity was expressed as ∆OD at 420/mg of activity has frequently been mentioned as a defense protein/ min. Peroxidase activity was measured as reaction of plants to pathogen attack. An increase in PAL described by “(Hammerschmidt and Kuc, 1982)”. Leaf activity results in increase in concentration of phenolic material was homogenized in 50mM sodium phosphate compounds, which are substrates for oxidative enzymes buffer, pH 6.8 (w/v, 1:1) centrifuged at 10,000 r.c.f for such as polyphenol oxidase and peroxidase. PAL 20 min at 4°C The reaction mixture contains 0.5mL of catalyzed first reaction of phenylproponoid pathway, enzyme extract, 1.5mL of substrate 0.05M pyrogallol phenylalanine to t-cinannamic acid, which results and 0.5mL 1% hydrogen peroxide, absorption was read accumulation of phenolics and other antimicrobial at 420nm was recorded at 30 seconds intervals for 2 compounds “(Slatnar et al., 2010)”. minutes, Enzyme activity was expressed as ∆OD at The highest activity of PPO was observed in 420/mg of protein/min. Catalase activity measured by EC-399299 (10.53, 12.56 and 13.10 ∆OD/mg of the method of “(Beers and Sizer, 1952)”. Leaf material protein/min) at 65DAS, 25DPI and 50DPI respectively was homogenized in 0.1M phosphate buffer, pH 6.5 followed by EC-399296 whereas lowest was observed (w/v, 1:1) centrifuged at 15,000r.c.f for 30 min at in Varuna, EC-399312 and EC-399302 throughout all 4°C.The reaction mixture contains 1.9 mL reagent stages. With the increase in infection and plant age, the grade water 1.0 mL of 0.059 M Hydrogen peroxide PPO activity was increased in all genotypes as shown which was incubate for 4-5 minutes to achieve in figure 3 and table 1. In the present investigation temperature equilibration and to establish blank rate, PPO activity was observed to be higher in infected add 0.1 mL of diluted enzyme and record decrease in leaves as comparison to the healthy one and the absorbance at 240 nm for 2-3 minutes. The difference resistant genotype expressed more PPO activity than in absorbance (∆A240) was divided by the H2O2 molar the susceptible one. Niranjanraj et al. (2006) observed extinction coefficient (36M-1.cm-1). Enzyme activity similar results that seedlings of resistant varieties had was expressed as µmol of H2O2/ mg of protein / min. greater PPO activity than susceptible seedlings. Total soluble proteins was estimated by “(Bradford Similarly the higher PPO activity was recorded in pearl 1976)”. millet tissues infected with DM fungus than healthy “(Shetty et al., 2001)”. Similar phenomenon has also RESULTS AND DISCUSSION been observed in pear fruits infected resistant cultivar In present investigation it was observed that with Erwinia amylovora pathogen “(Honty et al., disease severity increased with the plant age and 2005)”. The PPO induction upon infection was found infection, in all the genotypes. The maximum disease in the pearl millet-Sclerospora graminicola and wheat- severity was observed in Varuna which was 37.41% Alternaria triticina interactions increase in the activity and 85.9% at 25 DPI and 50DPI respectively followed level of polyphenol oxidase (PPO) was observed, this by EC-3399302, 85.59% and EC-399312, 80.8% at 50 could be enhanced the oxidation of phenolic DPI. No disease symptoms were observed at 65 DAS. compounds into the more toxic forms, quinones, Other genotypes were expressing a moderate level of against pathogen “(Tyagi et al., 2000)”. tolerance against A. brassicae figure 1 and table 1. The It was observed that Peroxidase activity was observation supported by the previous research on increased, as disease progressed. At 65DAS the lowest different genotypes of mustard infected by A. brassicae, activity was observed in Varuna and EC-399312 which concluded that Varuna, EC-399302 and EC-399312 was 11.31 and 11.08 ∆OD at 420nm/mg of protein/min were susceptible, other genotypes were highly or respectively. The lowest value was observed in Varuna moderately tolerant “(Patni et al., 2005)”. which was11.84 and 13.80 (∆OD at 420nm/mg of Progressive increase of PAL activity recorded protein/min) at 25DPI and 50DPI respectively whereas with increase in disease infection at 65DAS, 25DPI highest value were recorded for EC-399296 and EC- and 50 DPI shown in figure 2 and table 1.